关于过滤操作的叙述正确的是[ ]
A.过滤后浑浊的滤液直接倒掉
B.液面要始终低于滤纸的边缘
C.过滤的过程中玻璃棒可以用来搅拌
D.漏斗下端的管口要紧靠烧杯内壁
答案:B
已知三棱柱ABC-A1B1C1的各条棱长都相等,且CC1⊥底面ABC,则异面直线BC1与AC所成角的余弦值为______.
Ask your friend to call me as soon as she ______ back tomorrow.[ ]
A. will come
B. comes
C. coming
D. came